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. Author manuscript; available in PMC: 2019 Jul 8.
Published in final edited form as: Nano Lett. 2019 May 10;19(6):3878–3885. doi: 10.1021/acs.nanolett.9b01057

Figure 1.

Figure 1.

a) Schematic of the energy level diagram and proposed upconversion scheme. Section of the periodic table that highlights the alkaline-earth elements (group 2) used in this study. b) Illustration of the core and core/shell synthesis for the MLnF UCNPs by decomposition of rare-earth (Ln) and alkaline-earth (M) trifluoroacetate precursors. For each host material, 5 aliquots of core/shell samples were taken with increasing shell thickness (CS1 to CS5). c-i) TEM images of the core UCNPs with size distribution and standard derivation from measuring more than 300 nanoparticles. j-p) TEM images of the core/shell UCNPs with thickest shell CS5. For UCNPs with cubic shape, the edge length was converted into a diameter to be more comparable to the diameter of the reference sample NaGdF.